1. Field of Invention
The invention relates to, in general, an evaporative-emissions system for an automotive vehicle and, in particular, an evaporative-emissions-leak tester and method for detecting an evaporative-emissions leak of fuel vapor from the evaporative-emissions system.
2. Description of Related Art
An automotive vehicle generally includes a fuel system having a fuel tank and fuel-delivery lines. The lines typically include a plurality of conduits and associated connections operatively interconnecting the tank with an internal-combustion engine. A fuel pump is used to deliver fuel under pressure from the tank to the engine via the lines. The vehicle is often powered using gasoline as the fuel. Gasoline is a volatile substance that generates gases that, if untreated, may be harmful to the environment. These gases are generally referred to as “evaporative emissions” and can escape from the fuel system through very small orifices that may present themselves throughout the system. Accordingly, various governmental authorities in respective countries throughout the world have long mandated that such vehicles include a system for preventing release into the atmosphere of untreated or non-combusted fuel vapor generated in the fuel system.
Therefore, a gasoline-powered automotive vehicle typically includes an evaporative-emissions system that is designed to effectively deal with the evaporative emissions. The vehicle typically undergoes a “dry-fuel system” (without fuel) test of the evaporative-emissions system at the assembly plant where the vehicle is assembled. If the vehicle does not pass the test, the vehicle is not fueled and remains at the plant to possibly be fueled later. However, if the vehicle passes the test, the vehicle is fueled. Once the vehicle is fueled, there is a need to precisely determine if the vehicle has a leak of at least a predetermined size—for example, about 0.015-inch-diameter “hole” size (or equivalent)—in the fuel system. If there is a leak, it may be necessary to pursue a more costly and time-consuming procedure of “smoke-testing” (used to pinpoint the location of the leak) or just a tightening/replacement of a fuel cap of the vehicle. In either case, it is desirable to determine if there is a leak in the fuel system.
However, on a vehicle having natural-vacuum-leak detection (NVLD), it is difficult to diagnose the vehicle with current after-sales resources, such as a motor-vehicle dealership. More specifically, these resources cannot quickly and precisely determine whether the vehicle has a leak in the fuel system of at least a predetermined size after the vehicle is sold and/or serviced. These resources cannot quickly and precisely also check to determine whether it is necessary to pursue smoke-testing or just a tightening/replacement of the fuel cap. These resources cannot also provide a solution to test the vehicle at the plant after it has received fuel.
Thus, there is a need in the related art for a low-cost tool and corresponding test for detecting an evaporative-emissions leak of fuel vapor from an automotive vehicle. There is a need in the related art for such a tool and test that also can quickly and precisely determine whether the vehicle has a leak in the fuel system of at least a predetermined size after the vehicle is sold and/or serviced. There is a need in the related art for such a tool and test that can quickly and precisely also check to determine whether it is necessary to pursue smoke-testing or just a tightening/replacement of the fuel cap. There is a need in the related art for such a tool and test that can also provide a solution to test the vehicle at the plant after it has received fuel.